Wordclock over s/pdif

I have a small setup: Logic, Firebox, Eureka with digital card. I have been around the horn several times as to what my options are for a better digital connection b'tween the pre and the FB and now I am wondering if there is any reason for it. How reliable is the wordclock over the s/pdif port? Will I see any sonic improvement by adding a wordclock option (which is also much more expensive)?

Additionally, I cannot slave the Eureka s/pdif to my Mac. Right now (at least with 10.3.8) it won't sync to an external clock source w/o an independant wordclock. With 10.3.9 I can't control the clock source and so I can't set my FB to slave to the Eureka. Ideas?

It really depends on the device outputting the clock to be honest. By far word clock would be the best choice as it's a dedicate clock and not a header in an audio path. That's how you get clock from digital audio sources, there's a bit status basically that is sent out which tells the receiving device the information it needs. With word clock it's only clock information.

The device itself, depending on the buffering and overall design, may make your audio worse. Remember this, some converters will happily degrade your audio!

In the end always try to use word clock. If all you have is SPDIF, you work with it till you can use word clock.

I will try to paint a little different figure here. It is very much about generalizations, and we all that in the specific case it might be very different.

1 - if you have no need for synchronizing several devices, if at all possible use the internal clock. This goes mostly for AD of course. The internal AD clock in almost all devices is several times better than what you get with an external clock. (Contrary to what some marketing people try to make you believe).

2 - if you transmit a signal to a DA for playback, it is not much use in having a separate word clock. SPDIF or ADAT is good enough for that. Especially in my mind (not quite tested in real world by me though) if you run on an optical cable.

3 - if you do word-clock, do it right. Use the T connectors and terminators (read the manual).